package com.sig.formes;

import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.FloatBuffer;
import java.nio.ShortBuffer;

import com.sig.opengl.MyGLRenderer;

import android.opengl.GLES20;

public class Square extends Forme{

	private final String vertexShaderCode =
			// This matrix member variable provides a hook to manipulate
			// the coordinates of the objects that use this vertex shader
			"uniform mat4 uMVPMatrix;" +

        "attribute vec4 vPosition;" +
        "void main() {" +
        // the matrix must be included as a modifier of gl_Position
        "  gl_Position = vPosition * uMVPMatrix;" +
        "}";

	private final String fragmentShaderCode =
			"precision mediump float;" +
					"uniform vec4 vColor;" +
					"void main() {" +
					"  gl_FragColor = vColor;" +
					"}";

	private final FloatBuffer vertexBuffer;
	private final ShortBuffer drawListBuffer;
	private final int mProgram;
	private int mPositionHandle;
	private int mColorHandle;
	private int mMVPMatrixHandle;

	// number of coordinates per vertex in this array
	static final int COORDS_PER_VERTEX = 3;
	static float squareCoords[] = { -0.5f,  0.5f, 0.0f,   // top left
		-0.5f, -0.5f, 0.0f,   // bottom left
		0.5f, -0.5f, 0.0f,   // bottom right
		0.5f,  0.5f, 0.0f }; // top right

	private final short drawOrder[] = { 0, 1, 2, 0, 2, 3 }; // order to draw vertices

	private final int vertexStride = COORDS_PER_VERTEX * 4; // 4 bytes per vertex

	public Square() {
		// initialize vertex byte buffer for shape coordinates
		ByteBuffer bb = ByteBuffer.allocateDirect(
				// (# of coordinate values * 4 bytes per float)
				squareCoords.length * 4);
		bb.order(ByteOrder.nativeOrder());
		vertexBuffer = bb.asFloatBuffer();
		vertexBuffer.put(squareCoords);
		vertexBuffer.position(0);

		// initialize byte buffer for the draw list
		ByteBuffer dlb = ByteBuffer.allocateDirect(
				// (# of coordinate values * 2 bytes per short)
				drawOrder.length * 2);
		dlb.order(ByteOrder.nativeOrder());
		drawListBuffer = dlb.asShortBuffer();
		drawListBuffer.put(drawOrder);
		drawListBuffer.position(0);

		// prepare shaders and OpenGL program
		int vertexShader = MyGLRenderer.loadShader(GLES20.GL_VERTEX_SHADER,
				vertexShaderCode);
		int fragmentShader = MyGLRenderer.loadShader(GLES20.GL_FRAGMENT_SHADER,
				fragmentShaderCode);

		mProgram = GLES20.glCreateProgram();             // create empty OpenGL Program
		GLES20.glAttachShader(mProgram, vertexShader);   // add the vertex shader to program
		GLES20.glAttachShader(mProgram, fragmentShader); // add the fragment shader to program
		GLES20.glLinkProgram(mProgram);                  // create OpenGL program executables
	}

	public void draw(float[] mvpMatrix) {
		super.draw(mvpMatrix);
		
		// Add program to OpenGL environment
		GLES20.glUseProgram(mProgram);

		// get handle to vertex shader's vPosition member
		mPositionHandle = GLES20.glGetAttribLocation(mProgram, "vPosition");

		// Enable a handle to the triangle vertices
		GLES20.glEnableVertexAttribArray(mPositionHandle);

		// Prepare the triangle coordinate data
		GLES20.glVertexAttribPointer(mPositionHandle, COORDS_PER_VERTEX,
				GLES20.GL_FLOAT, false,
				vertexStride, vertexBuffer);

		// get handle to fragment shader's vColor member
		mColorHandle = GLES20.glGetUniformLocation(mProgram, "vColor");

		// Set color for drawing the triangle
		GLES20.glUniform4fv(mColorHandle, 1, color, 0);

		// get handle to shape's transformation matrix
		mMVPMatrixHandle = GLES20.glGetUniformLocation(mProgram, "uMVPMatrix");
		MyGLRenderer.checkGlError("glGetUniformLocation");

		// Apply the projection and view transformation
		GLES20.glUniformMatrix4fv(mMVPMatrixHandle, 1, false, mvpMatrix, 0);
		MyGLRenderer.checkGlError("glUniformMatrix4fv");

		// Draw the square
		GLES20.glDrawElements(GLES20.GL_TRIANGLES, drawOrder.length,
				GLES20.GL_UNSIGNED_SHORT, drawListBuffer);

		// Disable vertex array
		GLES20.glDisableVertexAttribArray(mPositionHandle);
	}
}